My cats are all microchipped, but they do wear safety collars too. The logic in that for me is that the collar is a visible clue (if they ever got out) that my cats are pets & not strays. A lot of people still don't know about microchips, unfortunately. Yes, they might lose the collar, but that's certainly better than getting hung up. And if they don't lose it, it's a clue for people to take a look at the tag and to return them to me. The microchip is a backup method, in case they end up at a shelter.
I read somewhere a long time ago about an ear tag, and thought that would be a great idea - a visible clue that the cat is a pet - but haven't seen anything more about that. Maybe it didn't work out for some reason?